package net.kloap.motg;

import android.content.Context;
import android.content.res.TypedArray;
import android.os.Parcel;
import android.os.Parcelable;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.widget.Scroller;

public class FlingAndScrollViewer extends ViewGroup {
	private Scroller mScroller;
	private VelocityTracker mVelocityTracker;
	private int mScrollX = 0;
	private int mCurrentScreen = 0;
	private float mLastMotionX;
	private static final String LOG_TAG = "FlingAndScrollViewer";
	private static final int SNAP_VELOCITY = 1000;
	private final static int TOUCH_STATE_REST = 0;
	private final static int TOUCH_STATE_SCROLLING = 1;
	private int mTouchState = TOUCH_STATE_REST;
	private int mTouchSlop = 0;

	public FlingAndScrollViewer(Context context) {
		super(context);
		mScroller = new Scroller(context);
		mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
		this.setLayoutParams(new ViewGroup.LayoutParams(
				ViewGroup.LayoutParams.WRAP_CONTENT,
				ViewGroup.LayoutParams.FILL_PARENT));
	}

	public FlingAndScrollViewer(Context context, AttributeSet attrs) {
		super(context, attrs);
		TypedArray a = getContext().obtainStyledAttributes(attrs,
				R.styleable.FlingAndScrollViewer);
		mCurrentScreen = a.getInteger(
				R.styleable.FlingAndScrollViewer_default_screen, 0);
		mScroller = new Scroller(context);
		mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
		this.setLayoutParams(new ViewGroup.LayoutParams(
				ViewGroup.LayoutParams.WRAP_CONTENT,
				ViewGroup.LayoutParams.FILL_PARENT));
	}

	public void setInitialPosition(int initialPosition) {
		mCurrentScreen = initialPosition;
	}

	@Override
	public boolean onInterceptTouchEvent(MotionEvent ev) {
		/*
		 * This method JUST determines whether we want to intercept the motion.
		 * If we return true, onTouchEvent will be called and we do the actual
		 * scrolling there.
		 */
		/*
		 * Shortcut the most recurring case: the user is in the dragging state
		 * and he is moving his finger. We want to intercept this motion.
		 */
		final int action = ev.getAction();
		if ((action == MotionEvent.ACTION_MOVE)
				& (mTouchState != TOUCH_STATE_REST)) {
			return true;
		}
		final float x = ev.getX();
		switch (action) {
		case MotionEvent.ACTION_MOVE:
			/*
			 * mIsBeingDragged == false, otherwise the shortcut would have
			 * caught it. Check whether the user has moved far enough from his
			 * original down touch.
			 */
			/*
			 * Locally do absolute value. mLastMotionX is set to the y value of
			 * the down event.
			 */
			final int xDiff = (int) Math.abs(x - mLastMotionX);
			boolean xMoved = xDiff > mTouchSlop;
			if (xMoved) {
				// Scroll if the user moved far enough along the X axis
				mTouchState = TOUCH_STATE_SCROLLING;
			}
			break;
		case MotionEvent.ACTION_DOWN:
			// Remember location of down touch
			mLastMotionX = x;
			/*
			 * If being flinged and user touches the screen, initiate drag;
			 * otherwise don't. mScroller.isFinished should be false when being
			 * flinged.
			 */
			mTouchState = mScroller.isFinished() ? TOUCH_STATE_REST
					: TOUCH_STATE_SCROLLING;
			break;
		case MotionEvent.ACTION_CANCEL:
		case MotionEvent.ACTION_UP:
			// Release the drag
			mTouchState = TOUCH_STATE_REST;
			break;
		}
		/*
		 * The only time we want to intercept motion events is if we are in the
		 * drag mode.
		 */
		return mTouchState != TOUCH_STATE_REST;
	}

	@Override
	public boolean onTouchEvent(MotionEvent event) {
		if (mVelocityTracker == null) {
			mVelocityTracker = VelocityTracker.obtain();
		}
		mVelocityTracker.addMovement(event);
		final int action = event.getAction();
		final float x = event.getX();
		switch (action) {
		case MotionEvent.ACTION_DOWN:
			Log.i(LOG_TAG, "event : down");
			/*
			 * If being flinged and user touches, stop the fling. isFinished
			 * will be false if being flinged.
			 */
			if (!mScroller.isFinished()) {
				mScroller.abortAnimation();
			}
			// Remember where the motion event started
			mLastMotionX = x;
			break;
		case MotionEvent.ACTION_MOVE:
			// Log.i(LOG_TAG,"event : move");
			// if (mTouchState == TOUCH_STATE_SCROLLING) {
			// Scroll to follow the motion event
			final int deltaX = (int) (mLastMotionX - x);
			mLastMotionX = x;
			// Log.i(LOG_TAG, "event : move, deltaX " + deltaX + ", mScrollX " +
			// mScrollX);
			if (deltaX < 0) {
				if (mScrollX > 0) {
					scrollBy(Math.max(-mScrollX, deltaX), 0);
				}
			} else if (deltaX > 0) {
				final int availableToScroll = getChildAt(getChildCount() - 1)
						.getRight() - mScrollX - getWidth();
				if (availableToScroll > 0) {
					scrollBy(Math.min(availableToScroll, deltaX), 0);
				}
			}
			// }
			break;
		case MotionEvent.ACTION_UP:
			Log.i(LOG_TAG, "event : up");
			// if (mTouchState == TOUCH_STATE_SCROLLING) {
			final VelocityTracker velocityTracker = mVelocityTracker;
			velocityTracker.computeCurrentVelocity(1000);
			int velocityX = (int) velocityTracker.getXVelocity();
			if (velocityX > SNAP_VELOCITY && mCurrentScreen > 0) {
				// Fling hard enough to move left
				snapToScreen(mCurrentScreen - 1);
			} else if (velocityX < -SNAP_VELOCITY
					&& mCurrentScreen < getChildCount() - 1) {
				// Fling hard enough to move right
				snapToScreen(mCurrentScreen + 1);
			} else {
				snapToDestination();
			}
			if (mVelocityTracker != null) {
				mVelocityTracker.recycle();
				mVelocityTracker = null;
			}
			// }
			mTouchState = TOUCH_STATE_REST;
			break;
		case MotionEvent.ACTION_CANCEL:
			Log.i(LOG_TAG, "event : cancel");
			mTouchState = TOUCH_STATE_REST;
		}
		mScrollX = this.getScrollX();
		return true;
	}

	private void snapToDestination() {
		final int screenWidth = getWidth();
		final int whichScreen = (mScrollX + (screenWidth / 2)) / screenWidth;
		Log.i(LOG_TAG, "from des");
		snapToScreen(whichScreen);
	}

	public void snapToScreen(int whichScreen) {
		Log.i(LOG_TAG, "snap To Screen " + whichScreen);
		mCurrentScreen = whichScreen;
		final int newX = whichScreen * getWidth();
		final int delta = newX - mScrollX;
		mScroller.startScroll(mScrollX, 0, delta, 0, Math.abs(delta) * 2);
		invalidate();
	}

	public void setToScreen(int whichScreen) {
		Log.i(LOG_TAG, "set To Screen " + whichScreen);
		mCurrentScreen = whichScreen;
		final int newX = whichScreen * getWidth();
		mScroller.startScroll(newX, 0, 0, 0, 10);
		invalidate();
	}

	@Override
	protected void onLayout(boolean changed, int l, int t, int r, int b) {
		int childLeft = 0;
		final int count = getChildCount();
		for (int i = 0; i < count; i++) {
			final View child = getChildAt(i);
			if (child.getVisibility() != View.GONE) {
				final int childWidth = child.getMeasuredWidth();
				child.layout(childLeft, 0, childLeft + childWidth,
						child.getMeasuredHeight());
				childLeft += childWidth;
			}
		}
	}

	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
		final int width = MeasureSpec.getSize(widthMeasureSpec);
		final int widthMode = MeasureSpec.getMode(widthMeasureSpec);
		if (widthMode != MeasureSpec.EXACTLY) {
			throw new IllegalStateException("error mode.");
		}
		final int heightMode = MeasureSpec.getMode(heightMeasureSpec);
		if (heightMode != MeasureSpec.EXACTLY) {
			throw new IllegalStateException("error mode.");
		}
		// The children are given the same width and height as the workspace
		final int count = getChildCount();
		for (int i = 0; i < count; i++) {
			getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);
		}
		Log.i(LOG_TAG, "moving to screen " + mCurrentScreen);
		scrollTo(mCurrentScreen * width, 0);
	}

	@Override
	public void computeScroll() {
		if (mScroller.computeScrollOffset()) {
			mScrollX = mScroller.getCurrX();
			scrollTo(mScrollX, 0);
			postInvalidate();
		}
	}

	/**
	 * Return the parceable instance to be saved
	 */
	@Override
	protected Parcelable onSaveInstanceState() {
		final SavedState state = new SavedState(super.onSaveInstanceState());
		state.currentScreen = mCurrentScreen;
		return state;
	}

	/**
	 * Restore the previous saved current screen
	 */
	@Override
	protected void onRestoreInstanceState(Parcelable state) {
		SavedState savedState = (SavedState) state;
		super.onRestoreInstanceState(savedState.getSuperState());
		if (savedState.currentScreen != -1) {
			mCurrentScreen = savedState.currentScreen;
		}
	}

	// ========================= INNER CLASSES ==============================
	public interface onViewChangedEvent {
		void onViewChange(int currentViewIndex);
	}

	/**
	 * A SavedState which save and load the current screen
	 */
	public static class SavedState extends BaseSavedState {
		int currentScreen = -1;

		/**
		 * Internal constructor
		 * 
		 * @param superState
		 */
		SavedState(Parcelable superState) {
			super(superState);
		}

		/**
		 * Private constructor
		 * 
		 * @param in
		 */
		private SavedState(Parcel in) {
			super(in);
			currentScreen = in.readInt();
		}

		/**
		 * Save the current screen
		 */
		@Override
		public void writeToParcel(Parcel out, int flags) {
			super.writeToParcel(out, flags);
			out.writeInt(currentScreen);
		}

		/**
		 * Return a Parcelable creator
		 */
		public static final Parcelable.Creator<SavedState> CREATOR = new Parcelable.Creator<SavedState>() {
			public SavedState createFromParcel(Parcel in) {
				return new SavedState(in);
			}

			public SavedState[] newArray(int size) {
				return new SavedState[size];
			}
		};
	}
}
